content: /*
   * Copyright 2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package hu.akarnokd.agera;
  
  import android.support.annotation.NonNull;
  
  import com.google.android.agera.Observable;
  import com.google.android.agera.Supplier;
  import com.google.android.agera.Updatable;
  
  /**
   * Defers the creation of the actual Observable till an Updatable registers.
   */
  final class AgeraDefer extends AgeraTracking<DeferUpdatable> {
  
      final Supplier<? extends Observable> supplier;
  
      AgeraDefer(Supplier<? extends Observable> supplier) {
          this.supplier = supplier;
      }
  
  
      @NonNull
      @Override
      protected DeferUpdatable createWrapper(@NonNull Updatable updatable) {
          Observable source = supplier.get();
          return new DeferUpdatable(updatable, source);
      }
  
      @Override
      protected void onAdd(@NonNull Updatable updatable, @NonNull DeferUpdatable wrapper) {
          wrapper.add();
      }
  
      @Override
      protected void onRemove(@NonNull Updatable updatable, @NonNull DeferUpdatable wrapper) {
          wrapper.remove();
      }
  }
  
  final class DeferUpdatable
  implements Updatable {
      final Updatable actual;
  
      final Observable source;
  
      DeferUpdatable(Updatable actual, Observable source) {
          this.actual = actual;
          this.source = source;
      }
  
      @Override
      public void update() {
          actual.update();
      }
  
      void add() {
          source.addUpdatable(this);
      }
  
      void remove() {
          source.removeUpdatable(this);
      }
  }
  